Field of the Invention
The present invention relates to a zoom lens and is suitable as an image pickup optical system of an image pickup apparatus such as a digital still camera, a video camera, a TV camera, or a monitoring camera.
Description of the Related Art
In recent years, a wide-angle type zoom lens is required to be short and compact, and to have a wide angle of view, large magnification and high optical performance (high resolution).
In the related art, there have been known, as zoom lenses that are small in size as the entire system and have a wide angle of view, negative lead type zoom lenses in which a lens unit having a negative refractive power is arranged closest to an object side. Of those negative lead type zoom lenses, there are known zoom lenses having a wide entire image pickup angle of view of from about 80° to about 110° (Japanese Patent Application Laid-Open Nos. 2008-046208 and 2008-233585).
In Japanese Patent Application Laid-Open No. 2008-046208, there is disclosed a zoom lens including a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, and a fourth lens unit having a positive refractive power, the zoom lens having an entire image pickup angle of view of 106° at a wide-angle end, a zoom ratio of about 2.1. In Japanese Patent Application Laid-Open No. 2008-233585, there is disclosed a zoom lens including a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a negative refractive power, a fourth lens unit having a positive refractive power, and a fifth lens unit having a positive refractive power, the zoom lens having an entire image pickup angle of view of 82° at a wide-angle end, and a zoom ratio of about 2.73.
In addition, there have been known, as zoom lenses that are small in size as the entire system and have a wide angle of view, positive lead type zoom lenses in which a lens unit having a positive refractive power is arranged closest to an object side (U.S. Patent Application Publication No. 2010/0302648). In U.S. Patent Application Publication No. 2010/0302648, there has been disclosed a zoom lens including, in order from the object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a positive refractive power, the zoom lens having an entire image pickup angle of view of 83° at a wide-angle end, and a zoom ratio of about 6.
In order to achieve a wide angle of view, downsizing of the entire system, and high resolution in a zoom lens, it is important to appropriately set lens configurations of respective lens units forming the zoom lens, refractive powers of the respective lens units, and a zoom type, for example.